『Abstract
　The speciation of dissolved organic phosphorus (DOP) in the temperate Tamar estuary of SW England is described. Eight stations from the riverine to marine end-members were sampled during four seasonal campaigns in 2007 and the DOP pool in the water column and sediment porewater was characterized and quantified using a flow injection manifold after sequential enzymatic hydrolysis. This enabled the enzymatically hydrolysable phosphorus (EHP) fraction and its component labile monoester phosphates, diester phosphates and a phytase-hydrolysable fraction that includes myo-inositol hexakisphosphate (phytic acid), to be determined and compared with the total DOP, dissolved reactive phosphorus (DRP) and total dissolved phosphorus (TDP) pools. The results showed that the DOP pool in the water column varied temporally and spatially within the estuary (1.1-22μg L^-1) and constituted 6-40％ of TDP. The EHP fraction of DOP ranged from 1.1-15μg L^-1 and represented a significant and potentially bioavailable phosphorus fraction. Furthermore the spatial profiles of the three components of the EHP pool generally showed non-conservative behavior along the salinity gradient, with apparent internal estuarine sources. Porewater profiles followed broadly similar trends but were notably higher at the marine station throughout the year. In contrast to soil organic phosphorus profiles, the labile monoester phosphate fraction was the largest component, with diester phosphates also prevalent. Phytic acid concentrations were higher in the lower estuary, possibly due to salinity induced desorption processes. The EHP fraction is not commonly determined in aquatic systems due to the lack of a suitable measurement technique and the Tamar results reported here have important implications for phosphorus biogeochemistry, estuarine ecology and the development of efficient strategies for limiting the effects of phosphorus on water quality.』

1. Introduction
2. Materials and methods
　2.1. Main characteristics of the study area
　　2.1.1. sampling and survey program
　2.2. Procedures and analytical methods
3. Results
　3.1. Dissolved reactive phosphorus (DRP), dissolved organic phosphorus (DOP) and total enzymatically hydrolysable phosphorus (EHP)
　3.2. The different classes of DOP
4. Discussion
　4.1. Dissolved organic phosphorus speciation in the Tamar estuary
　4.2. Internal cycling
　4.3. Seasonal and spatial variability
　4.4. Salinity gradient effects
5. Concluding remarks
Acknowledgments
References

DOP＝dissolved organic phosphorus（溶存有機リン）＝6-40％TDP
EHP＝enzymatically hydrolysable phosphorus（酵素で加水分解可能なリン）＝monoester phosphates（主要成分）＋diester phosphates＋phytase（フィターゼ）-hydrolysable phosphates（myo-inositol hexakisphosphate（phytic acid（フィチン酸））（イノシトール六リン酸分解酵素））＝DOPの生物利用可能な主要成分
DRP＝dissolved reactive phosphorus（溶存反応性リン）
TDP＝total dissolved phosphorus（全溶存リン）